Display device and method of manufacturing the same

ABSTRACT

A display device formed by plural pixels that have reflective regions and transmissive regions is disclosed. The display device includes, in each of the pixels: an element layer formed on a substrate; a planarizing layer formed on the substrate to cover the element layer; and a gap adjusting layer formed on the planarizing layer on the element layer. In the display device, the reflective region is formed by an area including the element layer, the planarizing layer, the gap adjusting layer, and a reflection electrode formed on the gap adjusting layer, and the transmissive region is formed by an area including the planarizing layer formed on the substrate excluding an area in which the gap adjusting layer is formed.

CROSS REFERENCES TO RELATED APPLICATIONS

The present invention contains subject matter related to Japanese PatentApplication JP 2006-342141 filed in the Japanese Patent Office on Dec.20, 2006, the entire contents of which being incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display device such as a liquidcrystal display device and a method of manufacturing the same.

2. Description of the Related Art

In recent years, liquid crystal display devices are used as displaydevices for various electronic apparatuses such as a personal computer,a cellular phone, and a digital camera by virtue of advantages that theliquid crystal display devices are thin and consume less power. Suchliquid crystal display devices are not self light-emitting displaydevices such as a CRT (Cathode Ray Tube) and an organicelectroluminescence (organic EL) device and are roughly divided into atransmissive type and a reflective type.

A transmissive liquid crystal display device performs display usinglight of a lighting device (a back light) arranged behind a liquidcrystal panel. A reflective liquid crystal display device performsdisplay using ambient light. Since the transmissive liquid crystaldisplay device performs display using light of the backlight, thetransmissive liquid crystal display device has an advantage that, evenif ambient light is weak, display at high luminance and contrast ispossible without being affected by the light. However, since thebacklight consumes almost a half of total power consumed by thetransmissive liquid crystal display device, it is difficult to reducepower consumption. Moreover, when ambient light is strong, display looksdark and viewability is deteriorated.

On the other hand, since the reflective liquid crystal display devicedoes not have a backlight, the reflective liquid crystal display devicehas an advantage that power consumption is extremely small. Thus, thereflective liquid crystal display device is effective as a displaydevice carried to the outdoor. However, the reflective liquid crystaldisplay device has a disadvantage that viewability is deteriorated in adark environment of use.

In order to solve the problems of the transmissive liquid crystaldisplay device and the reflective liquid crystal display device, asemi-transmissive (transflective) liquid crystal display device thatuses both transmissive-type display and reflective-type display isproposed (see, for example, JP-A-2001-318377).

The semi-transmissive liquid crystal display device performs displayusing ambient light when the environment is bright and performs displayusing a backlight when the environment is dark. For improvement of thecharacteristics, when the semi-transmissive liquid crystal displaydevice has both a reflective region and a transmissive region, thethickness of a liquid crystal layer of the transmissive region isdesigned to be about twice as large as the thickness of a liquid crystallayer of the reflective region.

As a kind of such a structure, a gap adjusting layer for adjusting thethickness of the liquid crystal layer of the reflective region isprovided on a side where a color filter is formed. When the gapadjusting layer is provided, bonding of the color filer and a thin filmtransistor (hereinafter referred to as TFT) has to be taken into accountto realize satisfactory characteristics. Thus, the reflective region isnarrowed (see, for example, JP-A-2005-115315) and reflectioncharacteristics are deteriorated.

When a mechanism for adjusting a gap is formed on the TFT side (see, forexample, JP-A-2001-350158), the bonding with the color filter isimproved. However, since the gap is adjusted by removing an insulatinglayer of the transmissive region, deterioration in a transmissionquality due to roughness formed by signal lines or the like is caused.Moreover, since a contact hole is opened in an insulating layer below areflection electrode, deterioration in the reflection characteristics iscaused.

SUMMARY OF THE INVENTION

As described above, when the gap adjusting layer for adjusting thethickness of the liquid crystal layer of the reflective region isprovided, a margin of bonding of the color filter and the thin filmtransistor (TFT) has to be taken into account to have excellenttransmission characteristics. Thus, the reflective region is narrowedand the reflection characteristics are deteriorated.

Therefore, it is desirable to improve the reflection characteristics andthe transmission characteristics.

According to an embodiment of the present invention, there is provided adisplay device formed by plural pixels that have reflective regions andtransmissive regions. The display device includes, in each of thepixels, an element layer formed on a substrate, a planarizing layerformed on the substrate to cover the element layer, and a gap adjustinglayer formed on the planarizing layer on the element layer. Thereflective region is formed by an area including the element layer, theplanarizing layer, the gap adjusting layer, and a reflection electrodeconnected to a pixel electrode at one end of the gap adjusting layer andformed on the gap adjusting layer. The transmissive region is formed byan area including the planarizing layer formed on the substrateexcluding an area in which the gap adjusting layer is formed.

In the display device, since the reflective region includes the gapadjusting layer in which the reflection electrode is formed, thereflective region can suppress deterioration in reflectioncharacteristics. Thus, it is possible to obtain a high reflectance. Thetransmissive region is formed by the area including the planarizinglayer formed on the substrate. The element layer in which a drivingtransistor, signal lines, and the like are formed is provided in thereflective region. Therefore, since the transmissive region does nothave items that block the transmission of light, such as signal lines,it is possible to realize a high transmission contrast ratio and hightransmittance.

According to another embodiment of the present invention, there isprovided a method of manufacturing a display device including the stepsof forming, on a substrate, a planarizing layer that covers an elementlayer formed on the substrate, forming, in the planarizing layer, acontact hole leading to the element layer, forming, in the planarizinglayer, a pixel electrode connected to the element layer through thecontact hole, forming a gap adjusting layer on the planarizing layer,and forming, on the gap adjusting layer, a reflection electrodeconnected to the pixel electrode at one end of the gap adjusting layer.

In the method of manufacturing the display device, since the gapadjusting layer in which the reflection electrode is formed is formed ina reflective region, the reflective region can suppress deterioration inreflection characteristics. Thus, it is possible to obtain a highreflectance. A transmissive region is formed by an area including theplanarizing layer formed on the substrate. The planarizing layer isformed in the transmissive region. Therefore, since roughness that causemissing of light due to signal lines and the like are not formed in thetransmissive region, it is possible to realize a high transmissioncontrast ratio and a high transmittance.

According to the embodiment of the present invention, since thereflective region can suppress deterioration in reflectioncharacteristics, it is possible to realize a display device having ahigh reflectance. Since the surface of the transmissive region is formedflat by the planarizing layer, it is possible to realize a displaydevice having a high transmission contrast ratio and a high reflectance.Since the reflection electrode is connected to the pixel electrode atone end of the gap adjusting layer, the contact hole connecting thereflection electrode and the pixel electrode is unnecessary. Therefore,the display device is excellent in reflection characteristics such as areflectance and a contrast. Moreover, since the gap adjusting layer isformed on the side where the element layer is formed, a step is formedon the element layer side. Therefore, since a margin of bonding with thecolor filer is unnecessary, when the transmittance is the same, thedisplay device is excellent in the reflection characteristics comparedwith the display device having the gap adjusting layer on the colorfilter side.

According to the still another embodiment of the present invention,since the reflective region can suppress deterioration in reflectioncharacteristics, it is possible to realize a display device having ahigh reflectance. Since the surface of the transmissive region is formedflat by the planarizing layer, it is possible to realize a displaydevice having a high transmission contrast ratio and a high reflectance.Since the reflection electrode is connected to the pixel electrode atone end of the gap adjusting layer, the contact hole connecting thereflection electrode and the pixel electrode is unnecessary. Therefore,the display device is excellent in reflection characteristics such as areflectance and a contrast. Moreover, since the gap adjusting layer isformed on the side where the element layer is formed, a step is formedon the element layer side. Therefore, since a margin of bonding with thecolor filer is unnecessary, when the transmittance is the same, thedisplay device is excellent in the reflection characteristics comparedwith the display device having the gap adjusting layer on the colorfilter side.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a plan view showing an element side substrate for one pixelof a liquid crystal cell of a liquid crystal display device according toa first embodiment of the present invention;

FIG. 1B is a sectional view taken along line A-A′ in FIG. 1A;

FIGS. 2A and 2B are main part sectional views showing an example of thestructure of a semi-transmissive liquid crystal display device in thepast as a comparative example 1;

FIGS. 3A and 3B are main part sectional views showing an example of thestructure of a semi-transmissive liquid crystal display device as acomparative example 2;

FIGS. 4A to 4C are manufacturing process sectional views showing amethod of manufacturing a liquid crystal display device according to thefirst embodiment;

FIGS. 5A and 5B are manufacturing process sectional views showing themethod of manufacturing a liquid crystal display device according to thefirst embodiment;

FIGS. 6A to 6C are manufacturing process sectional views showing amethod of manufacturing a liquid crystal display device according to asecond embodiment of the present invention;

FIG. 7 is a graph of a relation between the occupancy of roughness andan inclination angle of the roughness;

FIG. 8 is a main part sectional view showing a liquid crystal displaydevice according to the second embodiment;

FIG. 9 is a main part sectional view showing a liquid crystal displaydevice according to a third embodiment of the present invention; and

FIG. 10 is a main part sectional view showing a liquid crystal displaydevice according to a fourth embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A display device according to a first embodiment of the presentinvention is explained with reference to FIGS. 1A and 1B. FIG. 1A is aplan view showing an element side substrate for one pixel of a liquidcrystal cell of a semi-transmissive liquid crystal display device as anexample of the display device. FIG. 1B is a sectional view taken alongline A-A′ in FIG. 1A.

As shown in FIGS. 1A and 1B, a liquid crystal display device 1 is formedby plural pixels 40, in each of which a liquid crystal layer 20 issealed between substrates 10 and 30 opposed to each other. Each of thepixels 40 has a reflective region 5 and a transmissive region 6 anddisplays an image. An element layer (including driving and controlelements and signal lines) 11 is formed on the substrate 10. Aplanarizing layer 12 is formed on the substrate 10 to cover the elementlayer 11. A pixel electrode 14 connected to the element layer 11 througha contact hole 13 is formed on the planarizing layer 12 on the elementlayer 11. A gap adjusting layer 15 is formed on the pixel electrode 14and above the element layer 11. An upper surface (on the liquid crystallayer 20 side) of the gap adjusting layer 15 is formed in an irregularshape and a reflection electrode 16 is formed thereon. The reflectionelectrode 16 is connected to the pixel electrode 14 at an end of the gapadjusting layer 15.

Therefore, the reflective region 5 is formed by an area including theelement layer 11, the planarizing layer 12 that covers the element layer11, the gap adjusting layer 15 formed on the planarizing layer 12 via apart of the pixel electrode 14, and the reflection electrode 16 formedon the gap adjusting layer 15. The transmissive region 6 is formed by anarea including the planarizing layer 12 and the pixel electrode 14formed on the substrate 10 excluding an area in which the gap adjustinglayer 15 is formed.

On the other hand, a color filter 31 is formed on the substrate 30 thatis an opposed substrate opposed to the substrate 10. A pixel electrode33 is formed on the surface of the color filter 31 via a planarizinglayer 32.

In the liquid crystal display device 1, the contact hole 13 between theelement layer 11 and the pixel electrode 14 is covered by a lower partof the gap adjusting layer 15, i.e., covered by the gap adjusting layer15. Thus, reflection characteristics of the reflective region 5 areimproved. Although the pixel electrode 14 is formed on the surface ofthe transmissive region 6, since the thickness of the pixel electrode 14is uniform, the transmissive region 6 has a form same as a form madeflat by a planarizing layer. Thus, even if a light blocking member isnot provided, there is no light leakage and a high transmission contrastratio is obtained.

An example of the structure of a semi-transmissive liquid crystaldisplay device in the past is explained as a comparative example 1 withreference to main part sectional views in FIGS. 2A and 2B.

As shown in FIG. 2A, a liquid crystal display device 101 is formed ofplural pixels 140, in each of which a liquid crystal layer 120 is sealedbetween substrates 110 and 130 opposed to each other. Each of the pixels140 has a reflective region 105 and a transmissive region 106 anddisplays an image. An element layer (including driving and controlelements and signal lines) 111 is formed on the substrate 110. A gapadjusting layer 115 is formed to cover the element layer 111. An uppersurface (on the liquid crystal layer 120 side) of the gap adjustinglayer 115 is formed in an irregular shape and a contact hole 113reaching the element layer 111 is formed in the gap adjusting layer 115.A pixel electrode 114 connected to the element layer 111 through thecontact hole 113 is formed on the substrate 110. A reflection electrode116 is formed on the gap adjusting layer 115 via the pixel electrode114.

On the other hand, a color filter 131 is formed on the substrate 130that is an opposed substrate opposed to the substrate 110. A pixelelectrode 133 is formed on the surface of the color filter 131 via aplanarizing layer 132.

In the structure in the comparative example 1, since the contact hole113 is formed in the reflective region 105, reflection characteristicsare deteriorated. As shown in FIG. 2B as a section of the transmissiveregion 106 in FIG. 2A, a transmission widow 119 is formed in theplanarizing layer 118 to form a multi-gap. Thus, a step is formed on theplanarizing layer 118 in the sections of signal lines 120 and atransmission contrast falls. When the sections of the signal lines 120are shielded from light, a transmittance falls.

An example of the structure of a semi-transmissive liquid crystaldisplay device is explained as a comparative example 2 with reference tomain part sectional views in FIGS. 3A and 3B.

As shown in FIG. 3A, a liquid crystal display device 201 is formed ofplural pixels 240, in each of which a liquid crystal layer 220 is sealedbetween substrates 210 and 230 opposed to each other. Each of the pixels240 has a reflective region 205 and a transmissive region 206 anddisplays an image. An element layer (including driving and controlelements and signal lines) 211 is formed on the substrate 210. Aninsulating film 212 is formed to cover the element layer 211. An uppersurface (on the liquid crystal layer 220 side) of the insulating film212 above the element layer 211 is formed in an irregular shape and acontact hole 213 reaching the element layer 211 is formed in theinsulating film 212. A pixel electrode 214 connected to the elementlayer 211 through the contact hole 213 is formed on the substrate 210. Areflection electrode 216 is formed on the upper surface of theinsulating film 212 above the element layer 211 via a part of the pixelelectrode 214.

On the other hand, a color filter 231 is formed on the substrate 230that is an opposed substrate opposed to the substrate 210. A pixelelectrode 233 is formed on the surface of the color filter 231 via aplanarizing layer 232. Moreover, a gap adjusting layer 115 is formed onthe pixel electrode 214 opposed to the element layer 211.

In the structure in the comparative example 2, as shown in FIG. 3B, apixel structure of the transmissive region 6 is the structure in whichthe planarized insulating film 212 that covers signal lines 235 on thesubstrate 210 is formed. Moreover, the surface of the insulating film212 is formed flat. Thus, the structure is the same as the structure ofthe liquid crystal display device 1 according to this embodiment andhigh transmission characteristics are obtained. However, it is necessaryto take into account a margin of bonding of the two substrates 210 and230. The gap adjusting layer 234 formed on the opposed substrate (thesubstrate 230) side with respect to the reflective region 205 is reducedin size. Thus, a reflectance falls as definition is higher. Further,since the contact hole 213 of the reflective region 205 is necessary,reflection characteristics are deteriorated.

On the other hand, in the liquid crystal display device 1 according tothis embodiment, since the pixel electrode 14 is connected to theelement layer 11 through the contact hole 13 formed in the planarizinglayer 12 and the gap adjusting layer 15 of the reflective region 5 isformed on the pixel electrode 14, it is unnecessary to form a contacthole in the gap adjusting layer 15. Therefore, reflectioncharacteristics are improved. Further, since the gap adjusting layer 15is formed on the element layer 11 side, it is unnecessary to secure amargin of bonding with the opposed side. Therefore, since the gapadjusting layer 15 of the reflective region 5 can be formed wide, highreflection characteristics are obtained.

Moreover, in the semi-transmissive liquid crystal display device havingthe structure in the comparative example 2, it is necessary to formroughness on the surface of the insulating film 234. Therefore, theinsulating film 234 needs to have heat resistance for preventing theinsulating film 234 from being reflowed to be flat in a heating process.As a result, a material of the insulating film 234 is limited. On theother hand, in the planarizing layer 12 adopted in the liquid crystaldisplay device 1 according to this embodiment, it is unnecessary to formroughness on the surface thereof. Therefore, combination with functionalmaterials such as a low dielectric constant material like alicyclicolefin resin or SOG and a high planarization material having low heatresistance is possible.

In the case of the semi-transmissive liquid crystal display devicehaving the structure in the past, the insulating film 234 needs to havecharacteristics such as a transmittance and insulating properties.However, the gap adjusting layer 15 does not need such a characteristic.Therefore, it is possible to obtain improvement of functions such asimprovement of productivity, high reliability, and a low dielectricconstant by adopting a high sensitivity material, a high planarizationmaterial, and the like.

Optical characteristics of the semi-transmissive liquid crystal displaydevice according to this embodiment and the semi-transmissive liquidcrystal display device having the structure in the past (the comparativeexample 2) were compared. A result of the comparison is shown in Table1.

TABLE 1 Pixels in the past Embodiment Transmission Transmittance 3.4 3.5characteristics (%) Transmission 103 100 contrast ratio ReflectionReflectance 1.9 3 characteristics (%) Reflection 2.9 8.4 contrast ratio

As shown in Table 1, the transmission characteristics were substantiallythe same in the liquid crystal display device 201 having the structurein the past (the comparative example 2) and the liquid crystal displaydevice 1 according to this embodiment. On the other hand, concerning thereflection characteristics, the reflectance was 1.9% in the liquidcrystal display device 201 in the comparative example 2 and thereflectance was 3% in the liquid crystal display device 1 according tothis embodiment. As a result, in the liquid crystal display device 1according to this embodiment, the reflectance was 1.5 times as high asthat of the liquid crystal display device 201 in the comparative example2. This is because a contact hole was not formed in the gap adjustinglayer 15 and, since there was no assembly margin, a reflection area wasincreased. Moreover, a reflection contrast ratio was extremely low inthe liquid crystal display device 201 in the comparative example 2because of light leakage due to the influence of a step in a bondingdeviation portion and because of the contact hole. On the other hand, inthe liquid crystal display device 1 according to this embodiment, areflection contrast ratio was about three times as high as that of theliquid crystal display device 201.

As described above, since the reflective region 5 includes the gapadjusting layer 15 in which the reflection electrode 16 is formed, thereflective region 5 can suppress deterioration in reflectioncharacteristics. Therefore, a high reflectance can be obtained. Thetransmissive region 6 is formed by the area including the planarizinglayer 12 formed on the substrate 10. The element layer 11 in which thedriving transistor, the signal lines, and the like are formed isprovided in the reflective region 5. Therefore, since there are no itemsthat block the transmission of light in the transmissive region 6, it ispossible to realize a high transmission contrast ratio and hightransmittance.

A method of manufacturing a liquid crystal display device according tothe first embodiment is explained with reference to manufacturingprocess sectional views in FIGS. 4A to 4C and FIGS. 5A and 5B. FIGS. 4Ato 4C and FIGS. 5A and 5B show a semi-transmissive liquid crystaldisplay device as an example of the liquid crystal display device.

As shown in FIG. 4A, the element layer 11 made of a TFT or the like andincluding a switching element, an auxiliary storage capacitor, a gateline, and a signal line is formed on the substrate (first substrate) 10.

As shown in FIG. 4B, in order to planarize roughness due to the elementlayer 11 and the signal lines (not shown), the planarizing layer 12 isformed on the substrate 10. The contact hole 13 leading to the elementlayer 11 is formed on the planarizing layer 12. A transparent resist canbe used for the planarizing layer 12. As such a resist, for example,there is PC315G manufactured by JSR Corporation. Alternatively, anacrylic organic film, alicyclic olefin resin, SOG, and the like can beused.

As shown in FIG. 4C, the pixel electrode 14 connected to the elementlayer 11 through the contact hole 13 is formed on the planarizing layer12 as an electrode of the transmissive region 6. The pixel electrode 14is formed by, for example, a transparent electrode of indium tin oxide(ITO) or the like.

As shown in FIG. 5A, the gap adjusting layer 15 is formed on theplanarizing layer 12 above the element layer 11 of the reflective region5. Since the pixel electrode 14 connected to the element layer 11 isformed earlier and, then, the gap adjusting layer 15 is formed in thisway, a contact hole leading to the element layer 11 is prevented frombeing formed in the gap adjusting layer 15. Therefore, excellentreflection characteristics are obtained.

When the gap adjusting layer 15 is formed, the gap adjusting layer 15 isexposed with an exposure amount that can expose only a surface layer ofthe gap adjusting layer 15 and developed to form roughness on the uppersurface of the gap adjusting layer 15 and, then, baking of the gapadjusting layer 15 is performed. Therefore, the roughness are formed ina rounded shape. This baking is performed at, for example, 220° C.

Thereafter, as shown in FIG. 5B, the reflection electrode 16 connectedto the pixel electrode 14 at an end of the gap adjusting layer 15 isformed on the gap adjusting layer 15. The reflection electrode 16 isformed of, for example, a metal material having a high reflectance. Themetal material is, for example, silver (Ag), aluminum (Al), or the like.Since the upper surface of the gap adjusting layer 15 is formed in theshape of the rounded roughness and the reflection electrode 16 is formedon the surface thereof in this way, it is possible to improve thereflection characteristics of the reflective region 5.

As a process after that, an orientation film is formed, substrates arebonded together using a seal material via a color filter in which aspacer is formed or via a spacer, and liquid crystal is injected betweenthe substrates to complete a liquid crystal cell. A phase differenceplate and a sheet polarizer are bonded to this liquid crystal cell tomanufacture the semi-transmissive liquid crystal display deviceaccording to this embodiment.

According to the method of manufacturing a liquid crystal display deviceaccording to the first embodiment, since the reflective region 5 cansuppress deterioration in the reflection characteristics, it is possibleto realize a liquid crystal display device having a high reflectance.Since the surface of the transmissive region 6 is planarized by theplanarizing layer 12, it is possible to realize a liquid crystal displaydevice having a high transmission contrast ratio and a high reflectance.Since the reflection electrode 16 is connected to the pixel electrode 14at one end of the gap adjusting layer 15, a contact hole connecting thereflection electrode 16 and the pixel electrode 14 is unnecessary.Therefore, it is possible to realize a liquid crystal display deviceexcellent in reflection characteristics such as a reflectance and acontrast. Moreover, since the gap adjusting layer 15 is formed on theside where the element layer 11 is formed, a step is formed on theelement layer 11 side. Therefore, a margin of bonding with the colorfilter is unnecessary. Consequently, when the transmittance is the same,it is possible to form a display device excellent in the reflectioncharacteristics compared with the display device having the gapadjusting layer on the color filter side.

In the method of manufacturing a liquid crystal display device accordingto the first embodiment, depending on a material forming the gapadjusting layer 15, an exposure amount may be large to hinderproductivity. When the thickness of a film forming the gap adjustinglayer 15 is large, since reflow of the gap adjusting layer 15 increases,formation of roughness necessary for obtaining satisfactory reflectioncharacteristics is hindered. Therefore, a method of manufacturing aliquid crystal display device for reducing the thickness of the gapadjusting layer 15 is provided. An example of the method ofmanufacturing a liquid crystal display device is explained withreference to manufacturing process sectional views in FIGS. 6A to 6C asa method of manufacturing a liquid crystal display device according to asecond embodiment of the present invention. FIGS. 6A to 6C show asemi-transmissive liquid crystal display device as an example of theliquid crystal display device.

As shown in FIG. 6A, the element layer 11 made of a TFT or the like andincluding switching elements, auxiliary storage capacitance lines, gatelines, and signal lines is formed on the substrate (first substrate) 10.Subsequently, the planarizing layer 12 is formed on the substrate 10 inorder to planarize roughness due to the element layer 11 and the signallines (not shown). The planarizing layer 12 is formed flat in thereflective region 5 and the transmissive region 6 and has a step at anend of the element layer 11. In other words, the planarizing layer 12 isformed such that the height from the surface of the substrate 10 to thesurface of the planarizing layer 12 in an area in which a gap adjustmentlayer is formed is larger than the height to the surface of theplanarizing layer 12 in an area in which the gap adjusting layer is notformed. The contact hole 13 leading to the element layer 11 is formed inthe planarizing layer 12. A transparent resist can be used for theplanarizing layer 12. As such a resist, for example, there is PC315Gmanufactured by JSR Corporation. Alternatively, an acrylic organic film,alicyclic olefin resin, SOG, and the like can be used.

The pixel electrode 14 connected to the element layer 11 through thecontact hole 13 is formed on the planarizing layer 12 as an electrode ofthe transmissive region 6. The pixel electrode 14 is formed by, forexample, a transparent electrode of indium tin oxide (ITO) or the like.

As shown in FIG. 6B, an insulating film 17 having a flat surface isformed on the planarizing layer 12 via the pixel electrode 14.

As shown in FIG. 6C, the gap adjusting layer 15 formed of the insulatingfilm 17 is formed on the planarizing layer 12 on the element layer 11 ofthe reflective region 5 by a lithography technique and an etchingtechnique or, when the insulating film 17 is a photosensitive film, by alithography technique (exposure, development, etc.). The pixel electrode14 connected to the element layer 11 is formed earlier and, then, thegap adjusting layer 15 is formed in this way. Therefore, a contact holeleading to the element layer 11 is prevented from being formed in thegap adjusting layer 15 and excellent reflection characteristics areobtained.

When the gap adjusting layer 15 is formed, the gap adjusting layer 15 isexposed with an exposure amount that can expose only a surface layer ofthe gap adjusting layer 15 (e.g., an exposure amount smaller than anexposure amount for forming a contact hole) and developed to formroughness on the upper surface of the gap adjusting layer 15 and, then,baking of the gap adjusting layer 15 is performed. Therefore, the roughupper surface includes a round shape. This baking is performed at, forexample, 220° C.

As explained above, the planarized surface of the insulating film 17 isexposed with an exposure amount smaller than an exposure amount forforming a contact hole and developed to form a step. In this case, it ispossible to form, with a small exposure amount, application thickness αof the insulating film 17 for forming the gap insulating film 15 becausethe height β of the gap adjusting layer 15, which is a step forobtaining an appropriate gap, is reduce simultaneously with theformation of the application thickness α.

Consequently, since reflow of a material forming the roughness is alsocontrolled, as shown in a graph showing a relation between an excavationamount of a transmissive region of a planarizing layer and aninclination angle of roughness, the inclination angle of roughness canbe controlled by the excavation amount. Therefore, it is possible tomanufacture a liquid crystal display device having reflectioncharacteristics optimum for the device.

A liquid crystal display device according to the second embodiment isexplained with reference to a main part sectional view in FIG. 8. FIG. 8shows a semi-transmissive liquid crystal display device as an example ofthe liquid crystal display device.

As shown in FIG. 8, the liquid crystal display device 1 is formed by theplural pixels 40, in each of which the liquid crystal layer 20 is sealedbetween the substrates 10 and 30 opposed to each other. Each of thepixels 40 has the reflective region 5 and the transmissive region 6 anddisplays an image. The element layer (including driving and controlelements and signal lines) 11 is formed on the substrate 10. Theplanarizing layer 12 is formed on the substrate 10 to cover the elementlayer 11. The pixel electrode 14 connected to the element layer 11through the contact hole 13 is formed on the planarizing layer 12 on theelement layer 11. The gap adjusting layer 15 is formed on the pixelelectrode 14 and above the element layer 11. The gap adjusting layer 15is formed by, for example, two layers of organic insulating films. Anupper surface (on the liquid crystal layer 20 side) of the gap adjustinglayer 15 is formed in an irregular shape and the reflection electrode 16is formed thereon. The reflection electrode 16 is connected to the pixelelectrode 14 at an end of the gap adjusting layer 15.

Therefore, the reflective region 5 is formed by an area including theelement layer 11, the planarizing layer 12 that covers the element layer11, the gap adjusting layer 15 formed on the planarizing layer 12 via apart of the pixel electrode 14, and the reflection electrode 16 formedon the gap adjusting layer 15. The transmissive region 6 is formed by anarea including the planarizing layer 12 and the pixel electrode 14formed on the substrate 10 excluding an area in which the gap adjustinglayer 15 is formed.

On the other hand, the color filter 31 is formed on the substrate 30that is an opposed substrate opposed to the substrate 10. The pixelelectrode 33 is formed on the surface of the color filter 31 via theplanarizing layer 32.

In the pixels in the past, there are the roughness due to the contacthole and the signal lines in the pixels in the reflection area and it isdifficult to continuously arrange the roughness for obtainingsatisfactory reflection characteristics. However, according to thisembodiment, since it is possible to continuously arrange pixelsincluding roughness, a display element having satisfactory reflectioncharacteristics is obtained. A flat area is indispensable forstabilization of a gap in a photo-spacer. Since the rough areas arecontinuously formed and the heights of the rough areas are uniform, itis possible to arrange the photo-spacer on the rough surface.

A liquid crystal display device according to a third embodiment of thepresent invention is explained with reference to a main part sectionalview in FIG. 9. FIG. 9 shows a semi-transmissive liquid crystal displaydevice as an example of the liquid crystal display device.

As shown in FIG. 9, the liquid crystal display device 1 is formed by theplural pixels 40, in each of which the liquid crystal layer 20 is sealedbetween the substrates 10 and 30 opposed to each other. Each of thepixels 40 has the reflective region 5 and the transmissive region 6 anddisplays an image. The element layer (including driving and controlelements and signal lines) 11 is formed on the substrate 10. Theplanarizing layer 12 is formed on the substrate 10 to cover the elementlayer 11. The pixel electrode 14 connected to the element layer 11through the contact hole 13 is formed on the planarizing layer 12 on theelement layer 11. The gap adjusting layer 15 is formed on the pixelelectrode 14 and above the element layer 11. An upper surface (on theliquid crystal layer 20 side) of the gap adjusting layer 15 is formed inan irregular shape. A contact hole 18 leading to the contact hole 13 isformed in the gap adjusting layer 15. The reflection electrode 16connected to the pixel electrode 14 through the contact hole 18 isformed on the surface of the gap adjusting layer 15. The reflectionelectrode 16 is connected to the pixel electrode 14 at an end of the gapadjusting layer 15.

Therefore, the reflective region 5 is formed by an area including theelement layer 11, the planarizing layer 12 that covers the element layer11, the gap adjusting layer 15 formed on the planarizing layer 12 via apart of the pixel electrode 14, and the reflection electrode 16 formedon the gap adjusting layer 15. The transmissive region 6 is formed by anarea including the planarizing layer 12 and the pixel electrode 14formed on the substrate 10 excluding an area in which the gap adjustinglayer 15 is formed.

On the other hand, the color filter 31 is formed on the substrate 30that is an opposed substrate opposed to the substrate 10. The pixelelectrode 33 is formed on the surface of the color filter 31 via theplanarizing layer 32.

A liquid crystal display device according to a fourth embodiment of thepresent invention is explained with reference to a main part sectionalview in FIG. 10. FIG. 10 shows a semi-transmissive liquid crystaldisplay device as an example of the liquid crystal display device.

As shown in FIG. 10, the liquid crystal display device 1 is formed bythe plural pixels 40, in each of which the liquid crystal layer 20 issealed between the substrates 10 and 30 opposed to each other. Each ofthe pixels 40 has the reflective region 5 and the transmissive region 6and displays an image. The element layer (including driving and controlelements and signal lines) 11 is formed on the substrate 10. Theplanarizing layer 12 is formed on the substrate 10 to cover the elementlayer 11. The gap adjusting layer 15 is formed on the planarizing layer12 on the element layer 11 and above the element layer 11. An uppersurface (on the liquid crystal layer 20 side) of the gap adjusting layer15 is formed in an irregular shape. A contact hole 19 leading to theelement layer 11 piercing through the planarizing layer 12 is formed inthe gap adjusting layer 15. The pixel electrode 14 connected to theelement layer 11 through the contact hole 19 is formed on the surface ofthe gap adjusting layer 15. The reflection electrode 16 is formed on thepixel electrode 14 in an area of the gap adjusting layer 15.

Therefore, the reflective region 5 is formed by an area including theelement layer 11, the planarizing layer 12 that covers the element layer11, the gap adjusting layer 15, a part of the pixel electrode 14connected to the element layer 11 piercing through the gap adjustinglayer 15 and the planarizing layer 12, and the reflection electrode 16formed on the gap adjusting layer 15. The transmissive region 6 isformed by an area including the planarizing layer 12 and the pixelelectrode 14 formed on the substrate 10 excluding an area in which thegap adjusting layer 15 is formed.

On the other hand, the color filter 31 is formed on the substrate 30that is an opposed substrate opposed to the substrate 10. The pixelelectrode 33 is formed on the surface of the color filter 31 via theplanarizing layer 32.

In the respective embodiments, the roughness formed on the upper surfaceof the gap adjusting layer 15 may be continuously formed among thepixels. A photo-spacer can be arranged on the surface of the roughness.

As in the liquid crystal display device in the past, since it isdifficult to increase a transmission contrast in the roughness of thesignal lines when there is the step on the element layer 11 side. Thus,if it is attempted to substantially block light and improve thecontrast, a transmittance falls. On the other hand, in the liquidcrystal display devices according to the embodiments, since the signallines are embedded in the planarizing layer 12, a display panelexcellent in transmission characteristics can be obtained. In the past,the insulating film for roughness forming the reflection electrode islimited to an insulating film having reflection characteristics made ofacrylic resin or the like. However, it is possible to select materialshaving various characteristics such as a low dielectric constantmaterial like SOG or alicyclic olefin resin.

In the respective embodiments, the liquid crystal display device isexplained as an example of the display device. However, it is alsopossible to obtain characteristics such as an improved function and animproved aperture by using the present invention in a display devicesuch as an organic electroluminescence device in which a pixel electrodehas a contact hole (a connecting section) connected to an element layer.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations, and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1. A display device with plural pixels that each have a reflectiveregion and a transmissive region and a liquid crystal layer, the displaydevice comprising, in each of the pixels: an element layer on asubstrate; a planarizing layer on the substrate to cover the elementlayer, the planarizing layer having a contact hole in communication withthe element layer; a pixel electrode provided on a portion of theplanarizing layer and a portion of the element layer, said pixelelectrode being bounded by a sidewall of the contact hole a gapadjusting layer on the planarizing layer; and a reflection electrode onthe gap adjusting layer; wherein, the reflective region is defined by anarea including the element layer, the planarizing layer, the gapadjusting layer, and the reflection electrode formed on the gapadjusting layer, the transmissive region is defined by an area includingthe planarizing layer formed on the substrate but excluding the gapadjusting layer, and a portion of the gap adjusting layer is containedwithin the contact hole, said contact hole being covered by the gapadjusting layer, and a height of the planarizing layer from thesubstrate on the element layer of the reflective region is higher than aheight of the planarizing layer from the substrate on the transmissiveregion.
 2. The display device according to claim 1, wherein theplanarizing layer is flat in each of the reflective region and thetransmissive region.
 3. The display device according to claim 1, whereinthe pixel electrode is connected to the element layer through a contacthole in the planarizing layer.
 4. The display device according to claim1, wherein the gap adjusting layer is on a pixel electrode, thereflection electrode is on the gap adjusting layer, and the reflectionelectrode is connected to the pixel electrode at an end of the gapadjusting layer.
 5. The display device according to claim 1, wherein asurface of the gap adjusting layer comprises an irregular shape.
 6. Thedisplay device according to claim 1, wherein the transmission regionexcludes an area in which the reflection electrode is formed.
 7. Thedisplay device according to claim 1, wherein a surface of the reflectionelectrode that faces away from the gap adjusting layer includes a roundshape.
 8. The display device according to claim 1, wherein the pixelelectrode has uniform thickness.
 9. A display device with plural pixelsthat each have a reflective region and a transmissive region and aliquid crystal layer, the display device comprising, in each of thepixels: an element layer on a substrate; a planarizing layer on thesubstrate to cover the element layer, the planarizing layer having acontact hole in communication with the element layer; a pixel electrodeprovided on a portion of the planarizing layer and a portion of theelement layer, said pixel electrode being bounded by a sidewall of thecontact hole a gap adjusting layer on the planarizing layer; and areflection electrode on the gap adjusting layer; wherein, the reflectiveregion is defined by an area including the element layer, theplanarizing layer, the gap adjusting layer, and the reflection electrodeformed on the gap adjusting layer, the transmissive region is defined byan area including the planarizing layer formed on the substrate butexcluding the gap adjusting layer, a portion of the gap adjusting layeris contained within the contact hole, said contact hole being covered bythe gap adjusting layer, the planarizing layer has uniform thickness,and a height of the planarizing layer from the substrate on the elementlayer of the reflective region is higher than a height of theplanarizing layer from the substrate on the transmissive region.
 10. Thedisplay device according to claim 9, wherein the gap adjustment layer isformed over the element layer where the height of the planarizing layeron the element layer is higher than the height of the planarizing layeron the transmissive region.